As a housing material for mobile devices (for example, notebook type or tablet type personal computers, mobile phones including smart phones, digital cameras, digital video cameras, and the like), a thermoplastic resin composition (for example, ABS resin, polycarbonate resin/ABS resin, polyamide resin, and the like), or a material obtained by reinforcing a thermoplastic resin composition with an inorganic filler has been widely used. As a method of manufacturing a mobile device housing, a method of molding a thermoplastic resin composition by injection molding is usually adopted.
In recent years, for the housing of mobile devices, it has been required to further reduce a thickness, to provide sufficient resistance to impact and load in a state of being placed in a bag or the like, to be unpainted for the purpose of cost reduction, and the like. In order to satisfy these requirements, a thermoplastic resin composition used for the housing is required to have not only high rigidity and mechanical strength (impact resistance, and the like) after processing into a molded article, but also high weld strength, heat resistance, and good moldability at the time of molding.
However, for example, since the rigidity of thermoplastic resin compositions such as an ABS resin, a polycarbonate resin/ABS resin, and a polyamide resin which are not reinforced by an inorganic filler is low after processing into a molded article, such thermoplastic resin compositions cannot cope with the requirement of reducing the thickness of the housing. In addition, polyamide resin has high hygroscopicity, and warpage, dimensional change, and appearance deterioration are likely to occur over time after molding.
Therefore, as a thermoplastic resin composition used for the housing, a reinforced thermoplastic resin composition having improved rigidity by adding an inorganic filler such as glass fiber or carbon fiber to an ABS resin or polycarbonate resin/ABS resin has been studied.
However, a reinforced thermoplastic resin composition containing an ABS resin or polycarbonate resin/ABS resin as a main component has high rigidity when formed into a molded article, and although the housing can be reduced in thickness, weld strength and impact resistance, when formed into the molded article, are insufficient. On the other hand, a reinforced thermoplastic resin composition containing a polyamide resin as the main component is excellent in weld strength after processing into a molded article, but cannot solve the above-described warpage problem. This is a problem caused by moisture absorption of the molded article after molding, and a solution to the above problem by devising a molding material has not yet been proposed.
As a reinforced thermoplastic resin composition capable of obtaining a molded article excellent in impact resistance, the following have been proposed.
(1) A reinforced thermoplastic resin composition containing an aromatic polycarbonate resin, a graft copolymer, a glass fiber surface-treated with a water-soluble polyurethane, a glycidyl ether unit-containing polymer, and a phosphate ester-based flame retardant (PTL 1).
(2) A reinforced thermoplastic resin composition containing an aromatic polycarbonate resin, a fibrous filler surface-treated with polyamide, and a lubricant having a carboxyl group (PTL 2).
As a reinforced thermoplastic resin composition capable of obtaining a molded article excellent in mechanical strength, the following have been proposed.
(3) A reinforced thermoplastic resin composition containing an aromatic polycarbonate resin, a thermoplastic polyester resin, a glass fiber surface-treated with a silane coupling agent and an epoxy resin, and a thermoplastic elastomeric polymer (PTL 3).
(4) A reinforced thermoplastic resin composition containing a polycarbonate resin, a rubber-containing polymer, and carbon fibers converged with a nylon-based sizing agent (PTL 4).